1. Field of the Invention
The present invention relates to a surface light source device and a liquid crystal display assembly.
2. Description of the Related Art
In a liquid crystal display, liquid crystal itself does not emit light. Thus, for example, a so-called direct-type surface light source device (backlight) that radiates light to a liquid crystal display is arranged on the back surface of the liquid crystal display. By causing liquid crystal cells constituting each pixel to operate as a kind of optical shutter (light valve), that is, by controlling the light transmittance of each pixel, the optical transmittance of light (for example, white light) emitted from the surface light source device is controlled, thus displaying an image. As liquid crystal displays are becoming larger, surface light source devices (backlights) are also becoming larger.
Some degree of heat generation is inevitable during the operation of a light source constituting a surface light source device. Therefore, as the surface light source device operates, its temperature rises. When heat radiation for the surface light source device (in other words, heat radiation for the light source constituting the surface light source device) is not sufficient, the temperature of the light source rises, which causes various problems. For instance, when a light emitting diode (LED) is used as the light source, the efficiency of light emission decreases as the temperature of the light source rises. Therefore, in the case of a surface light source device having a plurality of light sources arranged therein, luminance or color variations occur as the temperature distribution becomes non-uniform in the surface light source device. Such luminance or color variations of the surface light source device cause a deterioration in the image quality of the liquid crystal display. Further, operating a light source under high temperature conditions is a cause of accelerated degradation of the light source. In view of this, various heat radiation measures have been proposed in the related art. For example, Japanese Unexamined Patent Application Publication No. 2006-59607 discloses a surface light source device in which a light source is arranged on a radiator plate to which a heat pipe and a heat sink are attached, and a cooling fan for promoting heat radiation of the heat sink is provided.